Abstract

Cigarette smoking is the main risk factor for the development of chronic obstructive pulmonary disease (COPD). An accelerated rate of lung function decline that causes clinically significant COPD, however, is present in only a minority of smokers. In addition to the cumulative amount of cigarettes smoked, other environmental and genetic properties contribute to this variable physiological response. This article reviews the role of airway hyperresponsiveness, mucus hypersecretion, infection, and proteases in the development of COPD.